It's a passing fad, it's just economics.
In larger urban centers land prices are going up, so density is increasing, and lawns are the first thing to shrink.
In smaller cities or even towns land prices are much lower so they typically still have big yards.
Sure bud. Look at any of the railroad towns that dot America and I guarantee you the yard sizes have remained small in the original area of town. We're seeing a return to form as car suburbs convert away from car dependency, rather the opposite trend of a century ago when streetcar suburbs were having their transit ripped out.
Only enthusiasts and professional vehicle operators want to drive everywhere for every trip. Everyone else wants things to be as simple as walking to the fridge. You don't get that with car dependency.
UNIX was not designed to stop you from doing stupid things, because that would also stop you from doing clever things. -- Doug Gwyn